Donor-Solvent-Dependent Cluster Formation of (C5Me5)SmI2(THF)x-Type Half-Sandwich Complexes

Structural Diversity and Multielectron Reduction Reactivity of Samarium(II) Iodido-β-diketiminate Complexes Dependent on Tetrahydrofuran Content

The molecular structures of complexes [Sm(Nacnac)I(thf)_n] (Nacnac = HC(C(Me)Ndipp)₂^-, dipp = 2,6-diisopropylphenyl, thf = tetrahydrofuran) depending on the number of thf ligands are studied. The complete removal of thf from a known complex [Sm(Nacnac)I(thf)₂] leads to a tetranuclear product [Sm(Nacnac)I]₄ (4). The partial removal of thf results in mixtures of dinuclear [Sm₂(Nacnac)₂I₂(thf)] (2), trinuclear [Sm₃(Nacnac)₃I₃(thf)] (3), and tetranuclear [Sm₄(Nacnac)₄I₄(thf)₂] (4*) complexes and 4, depending on the conditions. The reaction of solvent-free SmI₂ with 1 equiv of K(Nacnac) results mainly in [Sm(Nacnac)₂] (1), while the interaction of 4 with certain amounts of thf allows obtaining pure 2 and 3 (with the admixture of 4*). Complex 4* is the exact dimer of 2, and both compounds are stable in solutions. Reactions with 3 and 4 as reductants are studied. 4 is oxidized by I₂ to stoichiometrically yield two products, mixed-valent tetranuclear [Sm₄(Nacnac)₄I₅] (5) and binuclear [Sm(Nacnac)I₂]₂ (6) complexes. In the reaction of 4 with ⁿBu₃PTe, a trinuclear complex [Sm₃(Nacnac)₃(μ-I)₃(μ₃-E)₂] (8, E = I or Te) is formed in small amounts, with the formation of 6 as the second product. 3 serves as a two-electron reductant in the reaction with ⁿBu₃PTe to yield a trinuclear complex [Sm₃(Nacnac)₃I₃(μ-Te₂)] (7). Complexes 2, 4, 4*, 5, 6, and 8 possess a unique flat Sm_xI_y core of heavy atoms, which is assumed to be a consequence of the Nacnac ligand geometry.

Nanoscale Organolanthanum Clusters: Nuclearity-Directing Role of Cyclopentadienyl and Halogenido Ligands

Tetramethylaluminato/halogenido(X) ligand exchange reactions in half-sandwich complexes [CpR La(AlMe4 )2 ] are feasible in non-coordinating solvents and provide access to large coordination clusters of the type [CpR LaX2 ]x . Incomplete exchange reactions generate the hexalanthanum clusters [CpR 6 La6 X8 (AlMe4 )4 ] (CpR =Cp*=C5 Me5 , X=I; CpR =Cp'=C5 H4 SiMe3 , X=Br, I). Treatment of [Cp*La(AlMe4 )2 ] with two equivalents Me3 SiI gave the nonalanthanum cluster [Cp*LaI2 ]9 , while the exhaustive reaction of [Cp'La(AlMe4 )2 ] with the halogenido transfer reagents Me3 GeX and Me3 SiX (X=I, Br, Cl) produced a series of monocyclopentadienyl rare-earth-metal clusters with distinct nuclearity. Depending on the halogenido ion size the homometallic clusters [Cp'LaCl2 ]10 and [Cp'LaX2 ]12 (X=Br, I) could be isolated, whereas different crystallization techniques led to the aggregation of clusters of distinct structural motifs, including the desilylated cyclopentadienyl-bridged cluster [(μ-Cp)2 Cp'8 La8 I14 ] and the heteroaluminato derivative [Cp'10 La10 Br18 (AlBr2 Me2 )2 ]. The use of the Cp' ancillary ligand facilitates cluster characterization by means of NMR spectroscopy.